Apta-nanosensors for detection and quantitative determination of acetamiprid - A pesticide residue in food and environment

Developments in food neonicotinoids detection: novel recognition strategies, advanced chemical sensing techniques, and recent applications

Neonicotinoid insecticides (NEOs) are a new class of neurotoxic pesticides primarily used for pest control on fruits and vegetables, cereals, and other crops after organophosphorus pesticides (OPPs), carbamate pesticides (CBPs), and pyrethroid pesticides. However, chronic abuse and illegal use have led to the contamination of food and water sources as well as damage to ecological and environmental systems. Long-term exposure to NEOs may pose potential risks to animals (especially bees) and even human health. Consequently, it is necessary to develop effective, robust, and rapid methods for NEOs detection. Specific recognition-based chemical sensing has been regarded as one of the most promising detection tools for NEOs due to their excellent selectivity, sensitivity, and robust interference resistance. In this review, we introduce the novel recognition strategies-enabled chemical sensing in food neonicotinoids detection in the past years (2017-2023). The properties and advantages of molecular imprinting recognition (MIR), host-guest recognition (HGR), electron-catalyzed recognition (ECR), immune recognition (IR), aptamer recognition (AR), and enzyme inhibition recognition (EIR) in the development of NEOs sensing platforms are discussed in detail. Recent applications of chemical sensing platforms in various food products, including fruits and vegetables, cereals, teas, honey, aquatic products, and others are highlighted. In addition, the future trends of applying chemical sensing with specific recognition strategies for NEOs analysis are discussed.

Pesticide biosensors: trends and progresses

Pesticides, chemical substances extensively employed in agriculture to optimize crop yields, pose potential risks to human and environmental health. Consequently, regulatory frameworks are in place to restrict pesticide residue concentrations in water intended for human consumption. These regulations are implemented to safeguard consumer safety and mitigate any adverse effects on the environment and public health. Although gas chromatography- and liquid chromatography-mass spectrometry (GC-MS and LC-MS) are highly efficient techniques for pesticide quantification, their use is not suitable for real-time monitoring due to the need for sophisticated laboratory pretreatment of samples prior to analysis. Since they would enable analyte detection with selectivity and sensitivity without sample pretreatment, biosensors appear as a promising alternative. These consist of a bioreceptor allowing for specific recognition of the target and of a detection platform, which translates the biological interaction into a measurable signal. As early detection systems remain urgently needed to promptly alert and act in case of pollution, we review here the biosensors described in the literature for pesticide detection to advance their development for use in the field.

Emerging Insights into the Use of Advanced Nanomaterials for the Electrochemiluminescence Biosensor of Pesticide Residues in Plant-Derived Foodstuff

Pesticides have an important role in rising the overall productivity and yield of agricultural foods by eliminating and controlling insects, pests, fungi, and various plant-related illnesses. However, the overuse of pesticides has caused pesticide pollution of water bodies and food products, along with disruption of environmental and ecological systems. In this regard, developing low-cost, simple, and rapid-detecting approaches for the accurate, rapid, efficient, and on-site screening of pesticide residues is an ongoing challenge. Electrochemiluminescence (ECL) possesses the benefits of great sensitivity, the capability to resolve several analytes using different emission wavelengths or redox potentials, and excellent control over the light radiation in time and space, making it a powerful strategy for sensing various pesticides. Cost-effective and simple ECL systems allow sensitive, selective, and accurate quantification of pesticides in agricultural fields. Particularly, the development and progress of nanomaterials, aptamer/antibody recognition, electric/photo-sensing, and their integration with electrochemiluminescence sensing technology has presented the hopeful potential in reporting the residual amounts of pesticides. Current trends in the application of nanoparticles are debated, with an emphasis on sensor substrates using aptamer, antibodies, enzymes, and molecularly imprinted polymers (MIPs). Different strategies are enclosed in labeled and label-free sensing along with luminescence determination approaches (signal-off, signal-on, and signal-switch modes). Finally, the recent challenges and upcoming prospects in this ground are also put forward.

A systematic review on the implementation of advanced and evolutionary biotechnological tools for efficient bioremediation of organophosphorus pesticides

Ever since the concept of bioremediation was introduced, microorganisms, microbial enzymes and plants have been used as principal elements for Organophosphate pesticide (OPP) bioremediation. The enzyme systems and genetic profile of these microbes have been studied deeply in past years. Plant growth promoting rhizobacteria (PGPR) are considered as one of the potential candidates for OPP bioremediation and has been widely used to stimulate the phytoremediation potential of plants. Constructed wetlands (CWs) in OPP biodegradation have brought new prospects to microcosm and mesocosm based remediation strategies. Application of synthetic biology has provided a new dimension to the field of OPP bioremediation by introducing concepts like, gene manipulation andediting, expression and regulation of catabolic enzymes, implementation of whole-cell based and enzyme based biosensor systems for the detection and monitoring of OPP pollution in both terrestrial and aquatic environment. System biology and bioinformatics tools have rendered significant knowledge regarding the genetic, enzymatic and biochemical aspects of microbes and plants thereby, helping researchers to analyze the mechanism of OPP biodegradation. Structural biology has provided significant conceptual information regarding OPP biodegradation pathways, structural and functional characterization of metabolites and enzymes, enzyme-pollutant interactions, etc. Therefore, this review discussed the prospects and challenges of most advanced and high throughput strategies implemented for OPP biodegradation. The review also established a comparative analysis of various bioremediation techniques and highlighted the interdependency among them. The review highly suggested the simultaneous implementation of more than one remediation strategy or a combinational approach creating an advantageous hybrid technique for OPP bioremediation.

Application of Biosensors, Sensors, and Tags in Intelligent Packaging Used for Food Products-A Review

The current development of science and the contemporary market, combined with high demands from consumers, force manufacturers and scientists to implement new solutions in various industries, including the packaging industry. The emergence of new solutions in the field of intelligent packaging has provided an opportunity to extend the quality of food products and ensures that food will not cause any harm to the consumer's health. Due to physical, chemical, or biological factors, the state of food may be subject to degradation. The degradation may occur because the packaging, i.e., the protective element of food products, may be damaged during storage, transport, or other logistic and sales activities. This is especially important since most food products are highly perishable, and the maintenance of the quality of a food product is the most critical issue in the entire supply chain. Given the importance of the topic, the main purpose of this article was to provide a general overview of the application of biosensors, sensors, and tags in intelligent packaging used for food products. A short history and the genesis of intelligent packaging are presented, and the individual possibilities of application of sensors, biosensors, gas sensors, and RFID tags, as well as nanotechnology, in the area of the packaging of food products are characterized.

Irradiation-Induced Synthesis of Ag/ZnO Nanostructures as Surface-Enhanced Raman Scattering Sensors for Sensitive Detection of the Pesticide Acetamiprid

Detecting pesticides using techniques that involve simple fabrication methods and conducting the detection at very low levels are challenging. Herein, we report the detection of acetamiprid at the quadrillionth level using surface-enhanced Raman scattering (SERS). The SERS chip comprises Ag nanoparticles deposited on a tetrapod structure of ZnO coated onto indium tin oxide glass (denoted as Ag@ZnO-ITO). Controlled Ag decoration of ZnO occurs via irradiation-induced synthesis. The morphology of the surface plays a significant role in achieving an enhanced SERS performance for acetamiprid detection. 4,4'-Dipyridyl (DPY) is used to investigate synthesis conditions for the chip, leading to an optimal irradiation time of 60 min. Furthermore, the enhancement factor for acetamiprid on Ag@ZnO-ITO is higher than 10⁷. These results demonstrate that SERS sensors have the potential for practical use in acetamiprid detection.

Overarching issues on relevant pesticide transformation products in the aquatic environment: A review

The intensification of agricultural production during the last decades has forced the rapid increase in the use of pesticides that finally end up in the aquatic environment. Albeit well-documented, pesticides continue to raise researchers' attention, because of their potential adverse impacts on the environment and, inevitably, humans. Once entering the aquatic bodies, pesticides undergo biotic and abiotic processes, resulting in transformation products (TPs) that sometimes are even more toxic than the parent compounds. A substantial shift of the scientific interest in the TPs of pesticides has been observed since their environmental fate, occurrence and toxicity is still in its formative stage. In an ongoing effort to expand the existing knowledge on the topic, several interesting works have been performed mostly in European countries, such as France, Germany, Italy, Switzerland, Greece, and Spain that counts the highest number of relevant publications. Pesticide TPs have been also studied to a lesser extent in Asia, North and South America. To this end, the main objective of this review is to delineate the global occurrence, fate, toxicity as well as the analytical challenges related to pesticide TPs in surface, ground, and wastewaters, with the view to contribute to a better understanding of the environmental problems related with TPs formation. The concentration levels of the TPs, ranging from the low ng/L to high μg/L scale and distributed worldwide. Ultimately, an attempt to predict the acute and chronic toxicity of TPs has been carried out with the aid of an in-silico approach based on ECOSAR, revealing increased chronic toxicity for the majority of the identified TPs, despite the change they underwent, while a small portion of them presented serious acute toxicity values.

Recent advances in nanoremediation: Carving sustainable solution to clean-up polluted agriculture soils

Agriculture is one of the foremost significant human activities, which symbolizes the key source for food, fuel and fibers. This activity results in a lot of ecological harms particularly with the excessive usage of chemical fertilizers and pesticides. Different agricultural practices have remained industrialized to advance food production, due to the growth in the world population and to meet the food demand through the routine use of more effective fertilizers and pesticides. Soil is intensely embellished by environmental contamination and it can be stated as "universal incline." Soil pollution usually occurs from sewage wastes, accidental discharges or as byproducts of chemical residues of unrestrained production of numerous materials. Soil pollution with hazardous materials alters the physical, chemical, and biological properties, causing undesirable changes in soil fertility and ecosystem. Engineered nanomaterials offer various solutions for remediation of contaminated soils. Engineered nanomaterial-enable technologies are able to prevent the uncontrolled release of harmful materials into the environment along with capabilities to combat soil and groundwater borne pollutants. Currently, nanobiotechnology signifies a hopeful attitude to advance agronomic production and remediate polluted soils. Studies have outlined the way of nanomaterial applications to restore the eminence of the environment and assist the detection of polluted sites, along with potential remedies. This review focuses on the latest developments in agricultural nanobiotechnology and the tools developed to combat soil or land and or terrestrial pollution, as well as the benefits of using these tools to increase soil fertility and reduce potential toxicity.

An ultra-sensitive dual-responsive aptasensor with combination of liquid crystal and intercalating dye molecules: A food toxin case study

Herein, a label-free aptasensor was designed through forming a double-stranded DNA skeleton on the glass substrate for ultrasensitive quantification of ochratoxin A (OTA) as a case study. The function fundament of the dual-responsive aptasensor was the perturbation of the vertical alignment of the liquid crystals (LCs) and intercalation of the SYBR Green I (SGI) dye molecules between the base pairs of the double-stranded DNA structure. The presence of OTA decomposed the double-stranded structure of DNA by releasing the OTA-specific aptamer from the sensing platform that induced an apparent alteration of the optical and fluorescent responses. The aptasensor specifically detected the ultra-low levels of OTA as 47.0E-9 pM (0.047 aM) and 34.0E-3 pM (34 fM) based on the polarized and fluorescent responses, respectively. The aptasensor monitored OTA in the coffee and grape drink samples. The aptasensor provides promising insight for manufacturing real-time, cost-effective, and portable sensing devices for food control usage.

Ultrasensitive and practical chemiluminescence sensing pesticide residue acetamiprid in agricultural products and environment: Combination of synergistically coupled co-amplifying signal and smart interface engineering

Practical detection of single-component pesticide residue at ultra-low concentrations in agricultural products and environment is very important for assessment of environmental risks and protection of human health. Herein, a practical and highly sensitive chemiluminescence (CL) sensing acetamiprid in agricultural products and environmental media was constructed based on the synergistic co-catalysis of graphene oxide (GO)/gold nanoparticles (AuNPs) nanocomposites for luminol CL reaction and the smart interface engineering. ss-DNA could inhibit co-catalysis of GO/AuNPs for luminol CL reaction. Once acetamiprid was added, aptamer conformation changed in dimension and synergistically catalytic amplification signal of GO/AuNPs was restored significantly. The limit of detection was 8.9 pM. High sensitivity could be due to strong signal amplification from synergistic catalysis of GO/AuNPs for CL reaction and perfect regulation of composite interface by DNA dimension. Moreover, the used GO/AuNPs could be stably stored for six months, which was superior to previously reported AuNPs (only half a month). The analysis exhibited excellent selectivity for acetamiprid. The detection results for real samples confirmed reliability in practical application. This analysis is an extremely useful method for monitoring pesticide residues in environment and agricultural products. Synergetic co-catalysis of GO/AuNPs and ingenious interface engineering provide important ideas for other biosensors.

Amplified detection signal at a photoelectrochemical aptasensor with a poly(diphenylbutadiene)-BiOBr heterojunction and Au-modified CeO2 octahedrons

A major aspect of this work is the synergistic application of a poly(diphenylbutadiene)-BiOBr composite and a gold nanoparticle-linked CeO₂ octahedron to develop a photoelectrochemical aptasensor with an easily measurable detection signal change. Specifically, poly(diphenylbutadiene) nanofiber-immobilised BiOBr flower-like microspheres were developed as a hybrid material with a heterojunction that facilitates high visible light absorption and efficient photo-generated charge separation, which are essential features for sensitive photoelectrochemical sensors. The model analyte acetamiprid was attached via its specific aptamer on the aptasensor. Separately, a gold nanoparticle-linked CeO₂ octahedron was strategically used to significantly diminish the photocurrent by impeding electron transfer at the aptasensor surface. After acetamiprid binding, the CeO₂ octahedrons were displaced from the aptasensor. This caused a weakened quenching effect and restored the photocurrent to accomplish an "on-off-on" detection mechanism. This photoelectrochemical aptasensor exhibited a detection limit of 0.05 pM over a linear range of 0.1 pM-10 μM acetamiprid. The use of an aptamer has provided good specificity to acetamiprid and anti-interference. In addition, an ∼5.8% relative standard deviation was estimated as the reproducibility of the photoelectrochemical aptasensor. Furthermore, nearly 90% of the initial photocurrent was still measurable after storing these aptasensors at room temperature for 4 weeks, demonstrating their stability.

A Review on Biosensors and Nanosensors Application in Agroecosystems

Previous decades have witnessed a lot of challenges that have provoked a dire need of ensuring global food security. The process of augmenting food production has made the agricultural ecosystems to face a lot of challenges like the persistence of residual particles of different pesticides, accretion of heavy metals, and contamination with toxic elemental particles which have negatively influenced the agricultural environment. The entry of such toxic elements into the human body via agricultural products engenders numerous health effects such as nerve and bone marrow disorders, metabolic disorders, infertility, disruption of biological functions at the cellular level, and respiratory and immunological diseases. The exigency for monitoring the agroecosystems can be appreciated by contemplating the reported 220,000 annual deaths due to toxic effects of residual pesticidal particles. The present practices employed for monitoring agroecosystems rely on techniques like gas chromatography, high-performance liquid chromatography, mass spectroscopy, etc. which have multiple constraints, being expensive, tedious with cumbersome protocol, demanding sophisticated appliances along with skilled personnel. The past couple of decades have witnessed a great expansion of the science of nanotechnology and this development has largely facilitated the development of modest, quick, and economically viable bio and nanosensors for detecting different entities contaminating the natural agroecosystems with an advantage of being innocuous to human health. The growth of nanotechnology has offered rapid development of bio and nanosensors for the detection of several composites which range from several metal ions, proteins, pesticides, to the detection of complete microorganisms. Therefore, the present review focuses on different bio and nanosensors employed for monitoring agricultural ecosystems and also trying to highlight the factor affecting their implementation from proof-of-concept to the commercialization stage.

A facile colorimetric aptasensor for low-cost chlorpyrifos detection utilizing gold nanoparticle aggregation induced by polyethyleneimine

A colorimetric aptasensor for chlorpyrifos detection utilizing the localized surface plasmon resonance (LSPR) of gold nanoparticle (AuNP) aggregates coupling with a specific aptamer and cationic polyethyleneimine (PEI) has been developed. The measurement principle is based on a remarkable characteristic of AuNPs that can change their colors under the aggregation and dispersion conditions, which enables a sensitive colorimetric detection. In the absence of chlorpyrifos, negatively charged phosphate backbones of the aptamer potentially interact with the cationic PEI, resulting in the red color appearance of the dispersed AuNPs, whereas, in the presence of chlorpyrifos, the aptamer binds explicitly to chlorpyrifos, consequently releasing cationic PEI. Uninteracted PEI induces AuNP aggregation, causing a color change from red to blue that can be observed through the naked eye. Under the optimized conditions, 6 nM PEI, 10 nM aptamer, and a pH buffer of 7.5, the colorimetric aptasensor gives a linear response in the range of 20-300 ng mL-1 with a low detection limit of 7.4 ng mL-1. The developed method has been successfully applied to complex sample analysis. The accuracy and precision of chlorpyrifos quantification in spiked samples, including tap water, pomelo, and longan samples, are in the acceptable criteria of method validation, indicating that the developed aptasensor can be utilized as an alternative analytical tool for chlorpyrifos determination in complex samples. This aptasensor provides advantages such as a simple procedure, low cost, short analysis time, and involving uncomplicated instruments. Moreover, it offers high sensitivity, selectivity, and stability.

A novel liquid crystal-based aptasensor for ultra-low detection of ochratoxin a using a π-shaped DNA structure: Promising for future on-site detection test strips

Ochratoxin A (OTA) as the most dangerous mycotoxin is produced by Aspergillus Ochraceus and Penicillium verrucosum. OTA can be found in beverages and foodstuffs that induces the teratogenic, nephrotoxic, carcinogenic, and immunosuppressive effects on humans. Hence, developing highly sensitive methods for its detection is of great importance. Herein, a novel aptasensor was designed for the label-free monitoring of the ultra-low OTA levels by a combination of the superiority of aptamers and long-range orientational order of liquid crystals (LCs). The aptasensing strategy was based on the conformational switch of the immobilized π-shaped DNA structure on the glass substrate in presence of the target. A shift in the orientation of LCs from random to homeotropic state led to the apparent alteration of the optical appearance of the aptasensor platform from bright to dark. The LC-based aptasensor especially detects OTA at the ultra-trace level as low as 0.63 aM with comparable selectivity. The aptasensor could detect OTA successfully in the grape juice, coffee, and human serum samples. The LC-based aptasensor paves a way for developing portable and real-time sensing probes with high performance for food safety control and clinical application.

A silver@gold nanoparticle tetrahedron biosensor for multiple pesticides detection based on surface-enhanced Raman scattering

The detection of multiple pesticides in food and environment is of great importance for human health and safety. In this study, the DNA backbone structure and Ag@Au nanoparticles (NPs) to construct a nano-tetrahedron with the help of the surface-enhanced Raman scattering (SERS) effect by controlling the formation of SERS hotspots and subsequently realized the simultaneous detection of multiple pesticides. The DNA aptamers corresponding to the three pesticides of profenofos, acetamiprid and carbendazim were embedded into the three edges of the DNA tetrahedral skeleton, and the tetrahedral corners were connected to modify the Ag@Au NPs with different Raman signaling molecules. When aptamers recognize the related pesticides, the DNA backbone is deformed. Then Ag@Au NPs approach to each other with SERS hotspots formed and the intensity of the Raman signal increased, realizing the detection of the pesticide content. The biosensor constructed from the SERS substrate with higher sensitivity and lower detection limit (profenofos: 0.0021 ng mL^-1; acetamiprid: 0.0046 ng mL^-1; carbendazim: 0.0061 ng mL^-1). The practicability of this proposed method was verified by adding the recovery rate detection and the accuracy of the method was examined by the analysis of the HPLC-MS method. The proposed SERS biosensor could distinguish and detect three pesticides in food and environmental samples with high sensitivity and low detection limit that can be used in practical applications.

A low-background fluorescent aptasensor for acetamiprid detection based on DNA three-way junction-formed G-quadruplexes and graphene oxide

A simple fluorescence detection platform has been established for acetamiprid assay based on DNA three-way junctions (TWJs), which can triple the fluorescence signal without any other amplification. It is designed with three single-stranded DNAs (ssDNA), each of which contains one-third or two-thirds of the G-quadruplex sequence at each end. Upon the addition of acetamiprid, the conformation of the aptamer-containing double-stranded DNA (dsDNA) changes from its original conformation and releases a strand of ssDNA. This ssDNA, with the other two ssDNAs, can assemble into DNA TWJs, and the three pairs of the branched ends of the DNA TWJs are adjacent to each other, allowing them to form three units of G-quadruplexes. Hence, the fluorescence of N-methyl mesoporphyrin IX (NMM) is lighted by the nascent G-quadruplexes. Graphene oxide (GO) is then added to minimize the detection background by absorbing the free NMM and non-target-induced ssDNA. The proposed strategy can assay acetamiprid in a wide linear range of 0-500 nM with a detection limit of 5.73 nM. More importantly, this assay platform demonstrates high potential for acetamiprid assay in food control and environmental monitoring.

Determination of acetamiprid using electrochemiluminescent aptasensor modified by MoS2QDs-PATP/PTCA and NH2-UiO-66

A novel aptasensor has been fabricated based on the resonance energy transform (RET) system from MoS₂QDs-PATP/PTCA (donor) to NH₂-UiO-66 (acceptor). The electrochemiluminescence (ECL) signal of PTCA was greatly amplified due to the decoration of MoS₂QDs-PATP, and the NH₂-UiO-66 was utilized to label the signal probe DNA (pDNA), which hybridizes with the exposed aptamer anchored on the surface of MoS₂QDs-PATP/PTCA. With the target acetamiprid, the specific binding of acetamiprid to aptamer causes the connection between the donor and the acceptor to be interrupted and produce an "on" ECL signal. Thus, an "off-on" ECL sensing platform for sensitive and selective acetamiprid assay was designed. Under the optimal condition, the ECL signal of the aptasensor was found to be linearly related to the logarithm of the acetamiprid concentration ranging from 0.1 fM to 0.1 μM with a detection limit of 0.064 fM. More importantly, the recovery rate of the ECL aptasensor was calculated to be 98.7 ~ 106% with a RSD lower 5.1% for the residual acetamiprid assay in real food samples, which indicated that the aptasensor has high potential for practical applications.

An ultrasensitive platform for PCB77 detection: New strategy for liquid crystal-based aptasensor fabrication

Polychlorinated biphenyls (PCBs) are considered persistent bio-accumulative toxicants which threats global food safety and environmental health. Traditional analytical techniques for detection of PCBs are time-consuming and they do not satisfy urgent need for rapid and accurate monitoring of these persistent pollutants. Biosensor technology may be promising in this respect. Here we demonstrate a novel liquid crystal (LC)-based aptasensing platform as a promising label-free and rapid biosensor for PCB77 detection. This novel molecular strategy utilize triple-helix molecular conformational switch which is mediated formation of duplex on sensing platform in presence of target. Duplex forming leads to optical change from dark to bright in a liquid crystal based aptasensor. The limit of quantification of the LC-aptasensor to PCB77 is 1.5 × 10^-5 μg/L with comparable selectivity. Besides, we also demonstrated that this system is able to detect PCB77 in tap water, environmental water and milk. This strategy has potential for label-free and portable detection of different targets without any aptamer sequence length restrictions.

Label-free hairpin-like aptamer and EIS-based practical, biostable sensor for acetamiprid detection

Acetamiprid (ACE) is a kind of broad-spectrum pesticide that has potential health risk to human beings. Aptamers (Ap-DNA (1)) have a great potential as analytical tools for pesticide detection. In this work, a label-free electrochemical sensing assay for ACE determination is presented by electrochemical impedance spectroscopy (EIS). And the specific binding model between ACE and Ap-DNA (1) was further investigated for the first time. Circular dichroism (CD) spectroscopy and EIS demonstrated that the single strand AP-DNA (1) first formed a loosely secondary structure in Tris-HClO₄ (20 mM, pH = 7.4), and then transformed into a more stable hairpin-like structure when incubated in binding buffer (B-buffer). The formed stem-loop bulge provides the specific capturing sites for ACE, forming ACE/AP-DNA (1) complex, and induced the R_CT (charge transfer resistance) increase between the solution-based redox probe [Fe(CN)₆]^3−/4− and the electrode surface. The change of ΔR_CT (charge transfer resistance change, ΔR_CT = R_CT(after)-R_CT(before)) is positively related to the ACE level. As a result, the AP-DNA (1) biosensor showed a high sensitivity with the ACE concentration range spanning from 5 nM to 200 mM and a detection limit of 1 nM. The impedimetric AP-DNA (1) sensor also showed good selectivity to ACE over other selected pesticides and exhbited excellent performance in environmental water and orange juice samples analysis, with spiked recoveries in the range of 85.8% to 93.4% in lake water and 83.7% to 89.4% in orange juice. With good performance characteristics of practicality, sensitivity and selectivity, the AP-DNA (1) sensor holds a promising application for the on-site ACE detection.

A syringe-aided apta-nanosensing method for colorimetric determination of acetamiprid

A syringe-aided apta-nanosensing method is reported for the colorimetric determination of acetamiprid. The method employs double-stranded (ds) DNA-conjugated gold nanoparticle@magnetic agarose beads, i.e., dsDNA-AuNP@MABs as peroxidase-mimicking composite probes, in which the aptamer is indirectly attached to the AuNP surface through its hybridization with complementary DNA (cDNA). Upon contact with the acetamiprid target, the probes can give perceptible color change due to the possible conformation switch from dsDNA's brush-like to cDNA's 'pancake' regime. An "air-spaced pumping" procedure using a syringe equipped with ring magnets as the operation platform was proposed to facilitate the magnetic separation of the sensing probes. Therefore, the analytical steps can be easily accomplished in a syringe, including probe loading, acetamiprid capture and magnetic separation from crude samples, chromogenic reagent loading and colorimetric visualization. Acetamiprid concentration down to 3.3 ppb can be easily identified by the naked eye. The final solution also can be transferred for quantitative measurement. Under spectrometer, the ratio of the absorbance at 652 nm in the presence and absence of acetamiprid (A/A₀) is linearly related to the acetamiprid concentration in the 0.4-4.5 ppb range. The limit of detection is calculated to be 0.24 ppb. Moreover, satisfactory recoveries ranging from 90.90 to 91.82% with relative standard deviations of ≤2.96% were obtained in analyzing real spiked samples.

Recent advances in computational methods for biosensor design

Biosensors are analytical tools with a great application in healthcare, food quality control, and environmental monitoring. They are of considerable interest to be designed by using cost-effective and efficient approaches. Designing biosensors with improved functionality or application in new target detection has been converted to a fast-growing field of biomedicine and biotechnology branches. Experimental efforts have led to valuable successes in the field of biosensor design; however, some deficiencies restrict their utilization for this purpose. Computational design of biosensors is introduced as a promising key to eliminate the gap. A set of reliable structure prediction of the biosensor segments, their stability, and accurate descriptors of molecular interactions are required to computationally design biosensors. In this review, we provide a comprehensive insight into the progress of computational methods to guide the design and development of biosensors, including molecular dynamics simulation, quantum mechanics calculations, molecular docking, virtual screening, and a combination of them as the hybrid methodologies. By relying on the recent advances in the computational methods, an opportunity emerged for them to be complementary or an alternative to the experimental methods in the field of biosensor design.

Immunomagnetic separation: An effective pretreatment technology for isolation and enrichment in food microorganisms detection

The high efficiency and accurate detection of foodborne pathogens and spoilage microorganisms in food are a task of great social, economic, and public health importance. However, the contamination levels of target bacteria in food samples are very low. Owing to the background interference of food ingredients and negative impact of nontarget flora, the establishment of efficient pretreatment techniques is very crucial for the detection of food microorganisms. With the significant advantages of high specificity and great separation efficiency, immunomagnetic separation (IMS) assay based on immunomagnetic particles (IMPs) has been considered as a powerful system for the separation and enrichment of target bacteria. This paper mainly focuses on the development of IMS as well as their application in food microorganisms detection. First, the basic principle of IMS in the concentration of food bacteria is presented. Second, the effect of different factors, including the sizes of magnetic particles (MPs), immobilization of antibody and operation parameters (the molar ratio of antibody to MPs, the amount of IMPs, incubation time, and bacteria concentration) on the immunocapture efficiency of IMPs are discussed. The performance of IMPs in different food samples is also evaluated. Finally, the combination of IMS and various kinds of detection methods (immunology-based methods, nucleic acid-based methods, fluorescence methods, and biosensors) to detect pathogenic and spoilage organisms is summarized. The challenges and future trends of IMS are also proposed. As an effective pretreatment technique, IMS can improve the detection sensitivity and shorten their testing time, thus exhibiting broad prospect in the field of food bacteria detection.

DNA functionalized metal and metal oxide nanoparticles: principles and recent advances in food safety detection

The frequent occurrence of food safety incidents has given rise to unprecedented concern about food contamination issues for both consumers and the industry. Various contaminations in food pose serious threats to food safety and human health. Many detection methods were studied to address the challenge. Recently, biosensors relying on deoxyribonucleic acid (DNA)-functionalized nanoparticles have been developed as an efficient and effective detection method. In the current review, the strategies for DNA assembly metal and metal oxide nanoparticles are elaborated, recent applications of the sensors based on DNA-functionalized nanoparticles in food contaminant detection are discussed. Pathogenic bacteria, heavy metal ions, mycotoxins, antibiotics, and pesticides are covered as food contaminants. Additionally, limitations and future trends of functionalized nanoparticles-based technology are also presented. The current review indicates that DNA-functionalized metal and metal oxide nanoparticles are a novel nanomaterial with unique biological and physical properties for developing electrochemical, fluorescent, colourimetric and surface-enhanced Raman spectroscopy (SERS) sensors, etc. Compared with conventional detection techniques, DNA-functionalized metal and metal oxide nanoparticles have considerable advantages with high accuracy, high specificity, micro-intelligence, and low cost. Nevertheless, the stability of these sensors and the limitations of real-time detection are still under discussion. Therefore, more tolerant, portable, and rapid DNA sensors should be developed to better the real-time monitoring of harmful contaminants.

Recent advances on functional nucleic acid-based biosensors for detection of food contaminants

It has seen increasing development of reliable, robust, and flexible biosensors for rapid food-safety analysis in the past few decades. Recently, functional nucleic acid-based biosensors have attracted attention because of their programmability, bottom-up characteristics, and structural switches. However, few systematic reviews devoted to categorizing the potential of DNA nanostructures and devices were found for detecting food contaminants. Hence, the applications of functional nucleic acid-based biosensors were reviewed for analyzing food contaminants, including foodborne pathogen bacteria, biotoxins, heavy metals, and et al. In addition to categorizing the various biosensors, multiple signal readout strategies, such as optical, electrochemical, and mass-based signals were also examined. Finally, the future changes and potential opportunities, as well as practical applications of functional nucleic acid-based biosensors were discussed.

Impedimetric Aptamer-Based Biosensors: Applications

Impedimetric aptamer-based biosensors show high potential for handheld devices and point-of-care tests. In this review, we report on recent advances in aptamer-based impedimetric biosensors for applications in biotechnology. We detail on analytes relevant in medical and environmental biotechnology as well as food control, for which aptamer-based impedimetric biosensors were developed. The reviewed biosensors are examined for their performance, including sensitivity, selectivity, response time, and real sample validation. Additionally, the benefits and challenges of impedimetric aptasensors are summarized.

A low-cost paper-based aptasensor for simultaneous trace-level monitoring of mercury (II) and silver (I) ions

Mercury (Hg²⁺) and silver (Ag⁺) ions possess the harmful effects on public health and environment that makes it essential to develop the sensing techniques with great sensitivity for the ions. Metal ions commonly coexist in the different biological and environmental systems. Hence, it is an urgent demand to design a simple method for the simultaneous detection of metal ions, peculiarly in the case of coexisting Hg²⁺ and Ag⁺. This study introduces a low-cost paper-based aptasensor to monitor Hg²⁺ and Ag⁺, simultaneously. The strategy of the sensing array is according to the conformational changes of Hg²⁺- and Ag⁺-specific aptamers and their release from the GO surface after the injection of the target sample on the sensing platform. Through monitoring the fluorescence recovery changes against the concentrations of the ions, Hg²⁺ and Ag⁺ can be determined as low as 1.33 and 1.01 pM. The paper-based aptasensor can simultaneously detect the ions within about 10 min. The aptasensor is applied prosperously to monitor Hg²⁺ and Ag⁺ in human serum, water, and milk. The designed aptasensor with the main advantages of simplicity and feasibility holds the supreme potential to develop a cost-effective sensing method for environmental monitoring, food control, and human diagnostics.

Nano-Biosensing Platforms for Detection of Cow's Milk Allergens: An Overview

Among prevalent food allergies, cow milk allergy (CMA) is most common and may persist throughout the life. The allergic individuals are exposed to a constant threat due to milk proteins' presence in uncounted food products like yogurt, cheese, and bakery items. The problem can be more severe due to cross-reactivity of the milk allergens in the food products due to homologous milk proteins of diverse species. This problem can be overcome by proper and reliable food labeling in order to ensure the life quality of allergic persons. Therefore, highly sensitive and accurate analytical techniques should be developed to detect the food allergens. Here, significant research advances in biosensors (specifically immunosensors and aptasensors) are reviewed for detection of the milk allergens. Different allergic proteins of cow milk are described here along with the analytical standard methods for their detection. Additionally, the commercial status of biosensors is also discussed in comparison to conventional techniques like enzyme-linked immunosorbent assay (ELISA). The development of novel biosensing mechanisms/kits for milk allergens detection is imperative from the perspective of enforcement of labeling regulations and directives keeping in view the sensitive individuals.

Structure-guided post-SELEX optimization of an ochratoxin A aptamer

SELEX is the cornerstone for aptamer research with broad applications in biosensors and medicine. To improve the affinity of selected aptamers, we propose a structure-guided post-SELEX approach, an optimization method based on the precise secondary structure of the aptamer–ligand complex. We demonstrate this approach using the Ochratoxin A (OTA) aptamer. Guided by the structure, we designed a new aptamer whose affinity is improved by more than 50-fold. We also determined the high-resolution NMR structure of the new aptamer-OTA complex and elucidated the discriminatory recognition mechanism of one atomic difference between two analogs, OTA and OTB. The aptamer forms an unusual hairpin structure containing an intramolecular triple helix, which is not seen in the previously determined aptamer complex. The π–π stacking, the hydrophobic interaction, hydrogen bonds and halogen bonds between OTA and the aptamer contribute to the recognition of OTA, and the halogen bonds play an important role in discriminating between OTA and OTB. Our results demonstrate that the structure-guided post-SELEX approach improves aptamers affinity. An improved OTA biosensor system might be developed using this new strategy.

Assembly of 6-aza-2-thiothymine on gold nanoparticles for selective and sensitive colorimetric detection of pencycuron in water and food samples

A facile and novel nanosensor analytical strategy was developed for the colorimetric detection of pencycuron fungicide in rice, potato, cabbage, and water samples based on the pencycuron-induced aggregation of 6-aza-2-thiothymine-functionalized gold nanoparticles (ATT-AuNPs). The ATT-AuNPs exhibited good stability and were characterized with UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectrometry, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential techniques. The addition of pencycuron facilitated strong non-covalent interactions (electrostatic, van der Waals, and H bonding) between pencycuron and ATT-AuNPs, inducing a significant red shift in the surface plasmon resonance (SPR) peak of ATT-AuNPs along with a color change from red to blue. A linear equation was established between absorption ratio (A₇₂₀/A₅₂₈) and pencycuron concentration (2.5-100 μM) with a correlation coefficient (R²) of 0.9915. The detection limit was calculated to be 0.42 μM, which was much lower than that of other analytical methods. The designed ATT-AuNP serves as a promising nanosensor for the rapid, simple, and selective label-free colorimetric detection of pencycuron in rice, potato, cabbage, and water samples, is highly sensitive, and does not require sophisticated instruments, tedious sample preparations, and time-consuming separation and pre-concentration procedures.

A label-free electrochemical aptasensor based on 3D porous CS/rGO/GCE for acetamiprid residue detection

A novel label-free electrochemical aptasensor was fabricated based on a three-dimensional porous electrode (3D-CS/rGO/GCE) for the detection of acetamiprid residues. The sensing signal was generated by the DNA itself. The porous electrode was prepared by electrodeposition in situ and characterized by scanning electron microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). These results indicated that the porous electrode has a uniform nanoporous structure, high active area, and excellent conductivity, leading to improve the transmission efficiency of current signals. The 3D-CS/rGO/GCE was used to increase a load of acetamiprid aptamer on the electrode. Meanwhile, DNA self-assembly strategy was used to further increase the DNA amounts. Thus the electrochemical current was amplified significantly due to increased phosphate group amounts by the above synergistic effect. The determination of acetamiprid residues using square wave voltammetry (SWV) showed good sensitivity, with the linear range from 0.1 pM to 0.1 μM and the detection limit was 71.2 fM. The label-free electrochemical aptasensor was also used to detect acetamiprid residues in tea samples with satisfactory results.

The investigation of the G-quadruplex aptamer selectivity to Pb2+ ion: a joint molecular dynamics simulation and density functional theory study

The aptamers with the ability to form a G-quadruplex structure can be stable in the presence of some ions. Hence, study of the interactions between such aptamers and ions can be beneficial to determine the highest selective aptamer toward an ion. In this article, molecular dynamics (MD) simulations and quantum mechanics (QM) calculations have been applied to investigate the selectivity of the T30695 aptamer toward Pb²⁺ in comparison with some ions. The Free Energy Landscape (FEL) analysis indicates that Pb²⁺ has remained inside the aptamer during the MD simulation, while the other ions have left it. The Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) binding energies prove that the conformational stability of the aptamer is the highest in the presence of Pb²⁺. According to the compaction parameters, the greatest compressed ion-aptamer complex, and hence, the highest ion-aptamer interaction have been induced in the presence of Pb²⁺. The contact maps clarify the closer contacts between the nucleotides of the aptamer in the presence of Pb²⁺. The density functional theory (DFT) results show that Pb²⁺ forms the most stable complex with the aptamer, which is consistent with the MD results. The QM calculations reveal that the N-H bonds and the O…H distances are the longest and the shortest, respectively, in the presence of Pb²⁺. The obtained results verify that the strongest hydrogen bonds (HBs), and hence, the most compressed aptamer structure are induced by Pb²⁺. Besides, atoms in molecules (AIM) and natural bond orbital (NBO) analyses confirm the results.Communicated by Ramaswamy H. Sarma.

Click Reaction-Mediated T2 Immunosensor for Ultrasensitive Detection of Pesticide Residues via Brush-like Nanostructure-Triggered Coordination Chemistry

We develop an ultrasensitive T₂-mediated immunosensor based on the coordination chemistry and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide andalkyne (CuAAC) and apply it for the detection of pesticide residues. We functionalize polyglutamic acid (PGA) on polystyrene to form a brush-like nanostructure that has a large loading capacity of Cu(II) through the coordination chemistry between PGA and Cu(II). Such a brush-like nanostructure could be used to chelate Cu(II) to modulate the CuAAC between azide-functionalized 1000 nm polystyrene (PS₁₀₀₀) and alkyne-functionalized 30 nm magnetic nanoparticles (MNP₃₀), and the MNP₃₀-PS₁₀₀₀ conjugate as a product of CuAAC can act as a magnetic probe in this T₂-based immunosensor. This click chemistry and coordination chemistry-mediated immunosensor allows for an ultrasensitive detection for chlorpyrifos residue (0.022 ng/mL), a 58-fold enhancement compared with that of enzyme-linked immunosorbent assay (1.28 ng/mL), providing a promising platform for detection of trace small molecules.

Design of a liquid crystal-based aptasensing platform for ultrasensitive detection of tetracycline

We develop a novel label-free liquid crystal (LC) aptasensor based on intrinsic properties of nematic LCs for ultra-sensitive detection of tetracycline. The aptasensor is assembled by immobilizing aptamers onto the glass slide modified with both homeotropic alignment and silane coupling agents. Designed aptasensor makes use of the target-induced aptamer conformational switching and disruption of the orientation of LCs which lead to an obvious change of the optical appearance from a dark to a bright response. We describe the optimized condition for maintaining the homeotropic orientation of LCs, which are suitable for the tetracycline detection. The average gray-scale intensities of polarizing optical microscopy images were calculated to quantitatively detect tetracycline concentrations. The aptasensor works especially at trace level of tetracycline as low as 0.5 pM. Moreover, the LC aptasensor was successfully used to detect tetracycline in the real milk sample. According to the results, the proposed LC aptasensor for tetracycline detection is simple, ultra-sensitive, label free and ease of preparation.

Simultaneous determination of 25 pesticides in Zizania latifolia by dispersive solid-phase extraction and liquid chromatography-tandem mass spectrometry

An improved quick, easy, cheap, effective, rugged, and safe (QuEChERS) method combined with ultrapressure liquid chromatography tandem mass spectrometric method (UPLC-MS/MS) was developed to simultaneously determine 25 pesticides in Zizania latifolia. The samples were extracted with methanol(MeOH) and 0.1% formic acid (80:20, v/v) and cleaned with C₁₈ absorbent and primary-secondary amine (PSA). LC separation was performed on a BEH C₁₈ UPLC column under the condition of gradient elution with the mobile phase consisted of 0.5% formic acid (10 mM ammonium acetate)/MeOH. External standard calibration method with matrix-matched was used for quantification, and good linearity was obtained over a concentration range of 0.5–100 μg/l, with correlation coefficients greater than 0.9901. The limit of detection (LOD) and the limit of quantitation (LOQ) of the 25 pesticides were in the range of 0.2–1.0 µg/kg and 0.5–3.3 µg/kg, respectively. The recoveries ranged from 72% to 118%, and the relative standard deviations (RSDs) were less than 20%. Thus, the proposed method is suitable for the simultaneous determination of 25 pesticides in Z. latifolia.

Recent progress in the development of recognition bioelements for polychlorinated biphenyls detection: Antibodies and aptamers

Polychlorinated biphenyls (PCBs) are persistent pollutants, which have expanded in foods and the environment. Detection of PCBs is considered essential due to recognized side-effects of PCBs on health and the public concerns in this regard. On the other hand, due to the trace levels of these organic chlorine compounds, reliable and sensitive assays must be developed. Recognition elements are essential parts of analytical detection assays and sensors of PCBs since these elements are involved in the selective identification of the analytes of interest. Understanding the fundamentals of the recognition elements of PCBs and the benefits of the sensor strategies result in the development of next-generation recognition devices. This review aimed to highlight the recent progress in the recognition elements as key parts of biosensors. We initially, focused on the developed antibody-based biosensors for the detection of PCBs, followed by discussing the aptamers as novel recognition elements. Furthermore, the recent advancement in the development of aptamer-based solid phase extractions has been evaluated. These findings could contribute to improving the design of commercial PCB-kits in the future.

An aptamer based aggregation assay for the neonicotinoid insecticide acetamiprid using fluorescent upconversion nanoparticles and DNA functionalized gold nanoparticles

An acetamiprid-binding aptamer (ABA), gold nanoparticles (AuNPs) and upconversion nanoparticles (UCNPs) are used in a colorimetric and fluorometric method for the ultrasensitive and selective detection of the pesticide acetamiprid. The ABA is first configured into a duplex with a complementary DNA covalently attached to AuNPs. The resulting dsDNA-functionalized AuNP probe is not stable in 0.15 M NaCl solution and aggregates. This causing the color to change from red to purple. In the presence of acetamiprid, the ABA undergoes a structural switch from a DNA duplex to an aptamer-acetamiprid complex and consequently dissociates from the AuNPs. The partially unhybridized AuNPs are stable against salt-induced aggregation and show red color. The ratio of absorbances at 524 nm (red) and 650 nm (purple blue) varies with the concentration of acetamiprid in the 0.025-10 μM concentration range. The colorimetric signal can be further amplified by introducing DNA-modified carboxylated UCNPs (silica-coated NaYF₄:Yb,Er) which display red and green fluorescence under 980 nm excitation. An inner filter effect occurs between DNA-modified UCNPs and dsDNA-modified AuNPs. The fluorometric assay is based on the measurement of the ratio of red (654 nm) and green (540 nm) fluorescence and works in the 0.025 to 1 μM acetamiprid concentration range and has a 0.36 nM detection limit (at a signal-to-noise ratio of 3). Because of the specificity of the aptamer, the assay is high selective. It was successfully used to quantify acetamiprid in contaminated real samples. Graphical abstract Schematic presentation of an upconversion fluorescent assay for acetamiprid. It involves the principle of analyte-triggered structural switch of aptamers, salt-induced AuNP aggregation, and signal amplification from UCNP.

Fluorometric label-free aptasensor for detection of the pesticide acetamiprid by using cationic carbon dots prepared with cetrimonium bromide

A fluorometric aptamer-based method is described for sensitive detection of the pesticide acetamiprid. Cationic carbon dots (cCDs) with blue fluorescence were synthesized from cetrimonium bromide (CTAB) by a hydrothermal method. In the presence of the acetamiprid aptamers with a negative charge, the aptamers bind to the surface of the cCDs due to electrostatic attraction. As a result, the fluorescence of the cCDs is quenched partially (the best measurement was done at excitation/emission wavelengths of 360/445 nm). If acetamiprid is added to the above system, the aptamer binds to acetamiprid as a target with strong and specific affinity. Therefore, fluorescence increases proportionally to the acetamiprid concentrations. The aptasensor has a detection limit of 0.3 nM with a dynamic range from 1.6 to 120 nM which reveals that the method is sensitive in comparison to the other techniques. The selectivity of the method towards various pesticides was also studied and found to be adequate. The sensor was applied for the determination of acetamiprid in (spiked) wastewater, tap water, and tomatoes to underpin its practicability. Graphical abstract Cationic CDs (cCDs) were synthesized from cetrimonium bromide by a hydrothermal method. The addition of the negatively charged acetamiprid aptamer to a solution containing cCDs, the cCDs will be coated by the aptamer. This causes the blue fluorescence of the cCDs partially is quenched. If acetamiprid (ACP) is then added, the aptamer will bind to acetamiprid with strong and specific affinity. Hence, fluorescence will be gradually restored.

Metal-organic framework (MOF-5) coated SERS active gold gratings: A platform for the selective detection of organic contaminants in soil

In this work, we proposed the functionalization of a surface plasmon-polariton (SPP)-supported gold grating surface with the metal-organic framework (MOF-5) for sensitive, selective and reproducible surface-enhanced Raman scattering (SERS) detection of organophosphorus pesticides. Homogeneous distribution of plasmon intensity along the Au grating surface ensures the high reproducibility of SERS results (deviation of Raman peak intensity does not exceed the 4% along the sample). The surface-assisted growth of thin MOF-5 film was accomplished in two steps procedure: (i) covalent grafting by 4-carboxyphenyl groups and (ii) the immersion of samples in the mother liquid of MOF-5. Proposed SERS chip proved itself to be a perfect analytical probe for the detection of organophosphorus pesticides with high reliability and low detection limit up to 10^-12 M. Moreover, selective detection and recognition of several relevant organic contaminants (azo-dye, mycotoxin, and pesticide) from the simulated soil was successfully demonstrated. All SERS measurements were performed using portable Raman spectrometer and can easily be expanded to environmental conditions. Our work combines the high affinity of organic contaminants to the MOF-5 with excellent plasmonic excitation on the surface plasmon-polariton supported structure and shows the way to the realization of closed-to-ideal analytical SERS chip.